Current decay of myotonia mutant channels.

The time constant of decay is altered in hNa_V1.4_F1705I compared to wild type hNa_V1.4 channels. (A) Superimposed normalized currents through wild type and hNa_V1.4_F1705I channels at test pulses of −30, −20, and −10 mV exhibiting slowing of current decay in the mutant channel. (B) The time constants of current decay of hNa_V1.4_F1705I channels are significantly different compared to wild type in the absence (p<0.05) or presence of 0.5 µM of Ca²⁺ (p<0.001). The inset is an expanded view −20 mV to 0 mV. (C) Raw current traces of hNa_V1.4_F1705I channels at RT and at 37°C. Currents were measured at −20 mV, in the same cell at different temperatures with 0.5 µM of Ca²⁺ in the pipette. (D) Plot of the time constants of current decay of wild type and hNa_V1.4_F1705I channels at RT and at 37°C in 0.5 µM of Ca²⁺. Paired measurements were made at RT and at 37°C. The current decay of hNa_V1.4_F1705I is significantly different at 37°C compared to RT (p<0.05). (E) Plot of the steady-state inactivation of hNa_V1.4_F1705I channels at 37°C in 0.5 µM of Ca²⁺. For comparison the steady-state inactivation of wild type and hNa_V1.4_F1705I from Figure 1E are re-plotted. The symbols are the same in plots B, D and E.